WM9714L_06 WOLFSON [Wolfson Microelectronics plc], WM9714L_06 Datasheet - Page 37

• Manufacturer Part Number: WM9714L_06
• Description: AC 97 Audio CODEC
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Pre-Production
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Figure 12 Microphone Input Circuit
The input pins used for the microphones are MIC1, MICCM, MIC2A and MIC2B. Note that input pins
MIC2A and MIC2B are multi-function inputs and must be configured for use as microphone inputs
when required. This is achieved using MICCMPSEL[1:0] in register 22h (see Table 23). The input to
microphone pre-amp A can be selected from any of the three microphone inputs MIC1, MIC2A and
MIC2B using MPASEL[1:0]. Each pre-amp has independent boost control from +12dB to +30dB in
four steps. This is controlled by MPABST[1:0] and MPBBST[1:0].
When not in use each microphone pre-amp can be powered down using the Powerdown register bits
MPA and MPB (register 3Eh, bits [1:0]). When disabled the inputs are tied to Vmid (for MIC2A and
MIC2B this only applies when they are selected as microphone inputs, otherwise they are left
floating).
Table 23 Microphone Pre-amp Control
22h
REGISTER
ADDRESS
MICCM
MIC2A
MIC2B
MIC1
15:14
13:12
11:10
9:8
BIT
MICCMPSEL
MPASEL
MPABST
MPBBST
LABEL
Vmid
Vmid
Vmid
13-12
22h:
00 = +12dB
11 = +30dB
00 = +12dB
11 = +30dB
22h:11-10
00
00
00
00
DEFAULT
22h:9-8
MICA
MICB
MIC2A and MIC2B pin configuration
00: MIC2A and MIC2B microphone inputs
01: MIC2A only
10: MIC2B only
11: neither
MPA pre-amp input select
00 : MIC1
01 : MIC2A
10 : MIC2B
11 : unused (do not select)
MPA pre-amp gain control
00 : +12dB
01 : +18dB
10 : +24dB
11 : +30dB
MPB pre-amp gain control
00 = +12dB
01 = +18dB
10 = +24dB
11 = +30dB
DESCRIPTION
PP Rev 3.0 June 2006
WM9714L
37